Speaker of the House Paul Ryan, R-Wis., points to boxes of petitions supporting the Republican tax reform bill that is set for a vote later this week as he arrives for a news conference on Capitol Hill in Washington, Tuesday, Nov. 14, 2017. (AP Photo/J. Scott Applewhite)

"I don't think it'll be easy. There are many ways, sadly, that this can go off the rails -- but I think virtually every Republican wants to get to yes."

Yet confounding the GOP's efforts to secure votes, even in their own party, is an estimate from the Congressional Budget Office that the Senate bill would increase the deficit by $1.4 trillion over the next decade.

On top of that, Democrats accuse Republicans of caring more about a calendar win than the bill's very real consequences.

"They're just ramming and jamming this thing through because they want to say they have a victory before we go home for the holiday," Rep. Dina Titus, D-Nev., said.

The measure is largely a partisan one, some lawmakers said.

"What we've seen instead is a purely partisan bill that doesn't provide relief to middle class families," Rep. Derek Kilmer, D-Wash., said. "At the same time, the vast, vast majority of the benefits would go to the wealthiest 1 percent of Americans."

Looking ahead, tax reform isn't the only thing on lawmakers' minds. Another deadline is fast approaching; this one, to fund the government.

Legislators have until December 8 to pass a budget -- or face a shutdown.